1. Field of the Invention
The present invention relates to a plasma display apparatus and a method of driving the same, and more particularly, to a plasma display apparatus, which improves discharge efficiency by enhancing waveforms of sustain pulses applied during the sustain period of the plasma display apparatus, and a method of driving the same.
2. Background of the Related Art
A Plasma Display Panel (hereinafter PDP) is a device to display a picture through excitation and light emission of a phosphor by a vacuum ultraviolet (VUV) generated at the time of discharging an inert mixture gas. The PDP has advantages in that it can be large-sized and thin-filmed, its manufacture is easy due to a simple structure, and luminance and light emission efficiency are higher than those in other flat display devices. Especially, an alternate current surface discharge PDP has advantages of a low voltage operation and a long life since a wall charge is accumulated on a surface at the time of a discharge and the accumulated chargers protects the electrodes from sputtering generated by the discharge.
The plasma display panel is a display device which is obtained by coating several requisite layers over two sheets of flat glass basically forming an upper substrate and a lower substrate and thereafter bonding them each other.
On the upper substrate, a scan electrode for selecting a scan electrode line at the time of driving and a sustain electrode for delivering a sustain signal in order to cause a surface discharge along with a selected cell are mounted. On the upper end of the scan and sustain electrodes, a dielectric layer and a dielectric protective layer are sequentially formed.
On the lower substrate, an address electrode for delivering a data signal is formed, and on the upper end of the address electrode, a dielectric layer is formed. Barrier ribs for partitioning a discharge space are sequentially provided on the upper end of the formed dielectric layer.
A phosphor is coated over the discharge space, and the phosphor is excited by a vacuum ultraviolet (VUV) generated from an inert mixture gas filled in the discharge space to emit light.
The plasma display panel is driven by being divided into a reset period for initializing the entire cells, an address period for selecting cells and a sustain period for causing a display discharge in the selected cells.
That is, one frame period is divided into a plurality of subfields having a different number of emission according to a luminance weight. Each of the subfields is divided into a reset period, an address period and a sustain period.
The sustain discharge of the AC surface-discharge PDP driven in the above manner requires a high voltage. Accordingly, an energy recovering apparatus is used for recovering a-voltage between the scan electrode Y and the sustain electrode Z, to thereby use the recovered voltage as a driving voltage upon the next discharge.
FIG. 1 is a view showing a plasma display apparatus having an energy recovery circuit 10 and a square wave supply circuit 20 that are formed for recovering the sustain discharge voltage.
The energy recovery circuit 10 includes a source capacitor Cs, an inductor L, a first switch Q1 for supplying energy stored in the source capacitor to a panel capacitor PANEL, and a second switch Q2 for recovering the energy from the panel capacitor.
The square wave supply circuit 20 includes a third switch for applying a sustain voltage to the panel capacitor and a fourth switch Q4 for dropping a voltage of the panel capacitor to a ground voltage.
Here, the panel capacitor equivalently denotes electrostatic capacitance formed between the scan electrode Y and the sustain electrode Z.
FIG. 2 is a waveform and timing diagram showing output waveforms of the plasma display apparatus as illustrated in FIG. 1.
Referring to FIG. 2, the first switch Q1 is turned on, thereby applying the energy stored in the source capacitor Cs to the panel capacitor and increasing the voltage, and the third switch is turned on, thereby maintaining the sustain voltage, whereupon a sustain discharge occurs.
Accordingly, when a sustain pulse of a square waveform is supplied, only one discharge occurs for a short time during the initial period of the sustain pulse. The amount of light generated in the discharge is proportional to the discharge time. By this, the conventional plasma display apparatus applied with a square wave during the sustain period has a disadvantage of having a low light emission efficiency because light emission occurs for a short time.